1. Field of the Invention
This invention relates to contacting apparatus for mass and heat transfer operations, and more particularly, to a liquid-gas, extended surface interphase fluid contact medium defined by multiple, shaped, tube-containing interlocking panels for distributing a falling liquid into a thin film in order to provide an extended liquid surface for gas contact with the liquid. Such gas-liquid contact is used in trickle filters, absorption towers, stripping units, cooling towers and other equipment for treating, heating or cooling gases and liquids by contact between the fluids. In order to maximize efficiency, the apparatus used for effecting such gas-liquid contact should be characterized by a high void volume to effect a low resistance to the flow of fluids, a large surface area per unit of volume and a low density in order to provide an extensive contact surface with minimum weight.
2. Description of the Prior Art
Various apparatus are known in the art for providing gas-liquid contact for the purpose of stripping gas of undesirable contaminants, cooling the gas, as in the case of cooling towers used to cool air and other unit operations where it is necessary or desirable to expose a large liquid area in a small volume or in a short distance. Of the prior art devices designed to effect such liquid-gas contact, among the most efficient are the corrugated contact structures, which are constructed of a plastic or paper material to achieve a desirable weight reduction and to satisfy the necessary high void volume and large surface area requirements. However, problems have been experienced with many of these prior art devices, in that the falling liquid tends to "channel" or flow in streams across many of the contact surfaces rather than to completely wet the surfaces. This condition creates dry areas in the structure and reduces contact efficiency. In addition, excessive resistance to the flow of gas upwardly has been encountered in some of the prior art fluid contact designs and many of these structures are not sufficiently strong to permit efficient maintenance.
Typical of the liquid-gas interfacing devices known in the prior art is the contacting arrangement for mass transfer operations disclosed in U.S. Pat. No. 4,107,241, to Roland Braun. This patent discloses a plurality of stacked contacting grates having a first set of parallel strips and a second set of laterally spaced strips arranged in angular relationship with respect to the first set and provided with projections which are stamped from each strip in order to provide a large wetting surface. The plates may be manufactured of metal or of a plastic material and in the latter case, may be formed by injection molding. Another liquid-gas contact device is disclosed in U.S. Pat. No. 3,830,684, to Maurice Hamon, which device includes a corrugated, sheet-type, liquid-gas contact apparatus which includes a plurality of ramp-like deformations which are said to reduce liquid channeling, particularly in the trough portions of the corrugations. Yet another prior art fluid-contact device is disclosed in U.S. Pat. No. 2,793,017, to Douglas E. Lake, entitled "Apparatus for Distributing Falling Liquid in Thin Films." The Lake invention as embodied in this patent includes an assembly of corrugated sheet elements in stacked relationship, to provide an extended fluid contact surface for use in such devices as trickle filters, cooling towers, absorption towers, and the like. According to the disclosure, the corrugated sheet elements can be manufactured from organic thermoplastic sheet material, including a polymer or copolymer of styrene. A similar gas-liquid contacting device is disclosed in U.S. Pat. No. 3,485,485, to Heinz Faigle, which "Cooling Screen" device is characterized by a plurality of sheets having a median longitudinal axis, with corrugations extending in the longitudinal direction on either side of this axis and offset from one another on either side of the longitudinal axis, such that when viewed transversely, the ridge of one of the corrugations is aligned with the valley of another corrugation, the ridges and valleys of the corrugations being equal; when viewed longitudinally, unimpeded passageways are formed between the adjacent sheets. U.S. Pat. No. 3,792,841, to Carl G. Munters discloses a contact apparatus for liquid and gas which includes a contact body having first and second sets of corrugated sheets arranged with the sheets of the first set disposed alternately with sheets of the second set. The sheet corrugations provide channels or passageways which penetrate the contact body from edge to edge, with both the horizontal and vertical components thereof defining a fluted configuration. Another fluid contact device is disclosed in U.S. Pat. No. 3,704,869, to Ronald Priestley, and includes packing sheets comprising spaced, parallel units, each of which is a sector of a hollow, corrugated tube, connected by planar portions of the sheets, the assembled sheets providing a regular array of hollow, corrugated tubes. U.S. Pat. No. 2,977,103, to L. R. Smith, et al, discloses a "Cooling Tower Structure" which includes a rectangular, box-like container, open at the top, the sides and bottom of the container formed of U-shaped wire members positioned by cooperating longitudinal wires. Solid metal sheets define the ends of the container and cooling plates or baffles are placed in the frame in parallel, spaced relationship to achieve the desired fluid contact.
One of the problems associated with many of the prior art liquid-gas interface structures is the relatively great weight of such devices and particularly those which are constructed of metal. Since the supporting structure which contains the contacting material must frequently support more than one layer of the material, the economics of constructing such an apparatus dictate in favor of using materials which are light in weight and yet which provide a high percentage of voids and a large surface area for contacting the liquid and gas. Another problem which is frequently apparent in the use of prior art liquid-gas interfacing apparatus is the lack of sufficient contact surface and voids, a condition which frequently results in an excessive pressure drop across the apparatus itself. In an ideal mass transfer device, the contacting arrangement should ensure that all surfaces available for mass transfer are approximately uniformly wetted and that the entire cross-section is traversed by the gases without unused spaces or voids, such that mass transfer is maximized, with an accompanying low pressure drop in the gas stream. Furthermore, the device should present a large, extended surface area for wetting by the liquid and the apparatus should be constructed of a wetting material which is light in weight and yet resistant to the corrosive effects of the gas and/or the water or liquid stream. As heretofore described, in many such prior art devices the incoming liquid stream has a tendency to channel or form streams as it traverses the contact apparatus and therefore, does not wet and cover the surfaces of the apparatus to a desired extent. This channeling of the incoming liquid greatly reduces the area available for mass transfer, or the interaction between the gas and the water or other fluid, and lowers the efficiency of the material used as the contacting medium. This undesirable operating condition also results in a substantial reduction in interface contact between the liquid and gas, with a consequential reduction in heat transfer between the fluids.
Accordingly, it is an object of this invention to provide a new and improved tubular matrix medium for effecting efficient contact between fluids and between a gas and a liquid in particular, which medium is characterized by a high percentage of voids, minimum pressure drop in the gas phase, reduced channeling of the downward flowing fluid and a large surface area for effecting good interphase contact between the fluid streams.
Another object of this invention is to provide a new and improved extended surface contact apparatus having multiple, tubular-shaped members in a repeating array for use in cooling or cleaning incoming gas by using a countercurrent, downward movement of water or other liquid, which apparatus is characterized by resistance to corrosion, lightness of weight and an accompanying high percentage of voids and wettable contact surface areas, the surface areas being designed and oriented in a matrix to minimize channeling of the liquid and maximize disposition of a film of liquid on the contact surfaces to maximize the gas-liquid contact efficiency.
A still further object of this invention is to provide a hew and improved, substantially inert contact medium shaped into interlocking panels for interface contact between a gas and a liquid, which medium is characterized by multiple tubular-shaped members arranged in spaced relationship in a matrix array of connecting members, or fins and is light in weight, resistant to corrosion and is further characterized by a high percentage of voids with minimum pressure drop in the gas and a large liquid-gas contact surface area and which can be utilized in substantially any application, including heat and mass transfer operations where contact between a liquid and a gas is desired.
Yet another object of this invention is to provide new and improved, interlocking, liquid-gas contactor panels of selected size and shape which are formed of a thermoplastic or thermoresin material such as polypropylene, and can be quickly and easily joined together in stacked and staggered end-to-end relationship by connecting tabs and rivet means and easily shaped for insertion in a tower, which panels are characterized by a plurality of tapered, thin wall tubes spaced in a regular, recurring, vertical pattern or array in a matrix of thin, tapered, connecting fins and are designed to promote efficient distribution of liquid across the inside and outside surfaces of the tubes and the fins and effect efficient mass and heat transfer between a falling liquid and a rising gas introduced into a tower or structure containing the panels.
Another object of the invention is to provide fluid-contact panels which are characterized by a vertically oriented array of tapered tubes connected by tapered, flat strips containing vertically oriented receiving apertures and cooperating rivets for joining the panels in stacked, staggered orientation and further including horizontally disposed tabs and receiving sockets for connecting the panels in end-to-end relationship.